The role of the phosphorylation of various proteins associated with the protein synthesizing complex in translational control is currently being examined. Phosphorylated initiation factors in intact reticulocytes and reticulocyte lysates have been identified by two-dimensional polyacrylamide gel electrophoresis. The protein kinases and phosphoprotein phosphatases modifying these factors have been identified and partially characterized. The aim of this study is a functional analysis of the phosphorylated components and an examination of the effects of these modifications on protein synthesis. This will be accomplished by analyzing the phosphorylated and dephosphorylated factors in conjunction with phosphorylated and dephosphorylated ribosomes in the partial reactions of protein synthesis. In addition, the pattern of proteins phosphorylated in whole cells and in cell lysates will be examined under a variety of conditions which stimulate and inhibit protein synthesis. Some of the metabolic effectors to be studied include cyclic AMP, cyclic GMP, hemin, sodium fluoride and 5S inhibitor RNA. The recently identified inhibitor RNA will be purified and analyzed.